TUESDAY, Jan. 31 (HealthDay News) -- A pre-pregnancy diet high in animal fat increases the risk that moms-to-be will develop gestational diabetes, a new study says.

"Our findings indicate that women who reduce the proportion of animal fat and cholesterol in their diets before pregnancy may lower their risk for gestational diabetes during pregnancy," senior author Dr. Cuilin Zhang, of the epidemiology branch at the U.S. National Institute of Child Health and Human Development, said in an NIH news release.

Researchers analyzed data from more than 13,000 women in the U.S. Nurses' Health Study II. The women were ages 22 to 45 when they enrolled in the study and provided information every few years about their health and lifestyle habits, such as the kinds of foods they ate.

About 6 percent said they had been diagnosed with gestational diabetes, a form of diabetes that occurs during pregnancy. Gestational diabetes increases the risk for certain pregnancy complications and health problems in newborns.

Women who consumed the most animal fat were nearly twice as likely to develop gestational diabetes as those who consumed the lowest amounts. Also, women who consumed the highest amounts of dietary cholesterol were 45 percent more likely to develop gestational diabetes than those who consumed the lowest amounts.

There was no increased risk of gestational diabetes among women whose diets were high in total fat or other kinds of fat, said the researchers at the NIH and Harvard University.

They also found that the increased risk for gestational diabetes associated with diets high in animal fat and cholesterol seemed to be independent of other dietary and non-dietary risk factors.

For example, exercise is known to reduce the risk of gestational diabetes. But among pregnant women who exercised, the risk of gestational diabetes was higher among those who consumed higher amounts of animal fat and cholesterol than those who consumed lower levels of those types of fat.

The researchers concluded that changing 5 percent of dietary calories from animal fat to plant-derived sources could reduce a woman's risk of gestational diabetes by 7 percent.

The study was published online Jan. 4 in the American Journal of Clinical Nutrition.

"This is the largest study to date of the effects of a pre-pregnancy diet on gestational diabetes," first author Katherine Bowers of the NICHD said in the news release. "Additional research may lead to increased understanding of how a mother's diet before and during pregnancy influences her metabolism during pregnancy, which may have important implications for the baby's health at birth and later in life."

While the study found an association between a high fat diet and gestational diabetes, it did not prove that such a diet causes the condition.